What is the design process of lost-flow mold for heavy-duty truck gearbox?


Release time:

2023-02-02

The EPC process can meet the above market requirements for heavy truck transmission boxes. Generally speaking, the more complex the box structure, the more the EPC process can play its advantages. However, the complex structure of the product and the problems in field use make the design and manufacture of the foaming mold of the heavy truck gearbox difficult. Taking the mold design of 9-speed heavy truck gearbox as an example, the relevant design and manufacturing process are introduced.

The EPC process can meet the above market requirements for heavy truck transmission boxes. Generally speaking, the more complex the box structure, the more the EPC process can play its advantages. However, the complex structure of the product and the problems in field use make the design and manufacture of the foaming mold of the heavy truck gearbox difficult. Taking the mold design of 9-speed heavy truck gearbox as an example, the relevant design and manufacturing process are introduced.

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1. There are six difficulties in the design of the gearbox mold: ① The wall thickness is 8mm, and the foam pattern is not easy to form; ② There is a partition in the middle, and there is a hole in the middle of the partition, so it is necessary to make a side core pulling movable block; ③ Both sides are open and the foam is easy to deform. ④ The product is closed on all sides and needs to be bonded and combined into two pieces. ⑥ Some products divided into two pieces produce reverse drawing die, the mold needs to make side core-pulling movable blocks.

2. The basic requirements of the gearbox mold

(1) The dimensional accuracy of the mold needs to make the casting within the accuracy range required by the drawing.

(2) The mold cavity and mold base have no casting defects, and the working surface roughness of the mold is ≤ Ra0.8 mm.

(3) In order to make the heating and cooling of the pattern uniform and fast, the mold material should have good thermal conductivity. The mold cavity is typically made of a thin shell conformal structure.

(4) The spray gun in the mold should be set to ensure smooth feeding, so that the preformed beads can smoothly fill all parts of the pattern.

(5) Set the position of the exhaust valve correctly and determine the size of the exhaust area to make the pattern compact and uniform heating and cooling.

(6) The mold should have sufficient strength and rigidity, good corrosion resistance to water, steam and other media, and long service life.

(7) The mold should be reliably connected with the molding machine, and the installation and positioning should be accurate.

(8) The mold is easy to manufacture and operate.

3. Mold process requirements

According to the above product structure, mold requirements and on-site use problems, from the perspective of white area mold production and black area casting, the design and manufacturing scheme of EPC mold for heavy truck gearbox was jointly determined with a mold company in Luoyang.

(1) Pattern parting According to the structural characteristics of the casting, the pattern is divided into two parts A and B along the center line of the three-axis hole. The mold parts are positioned with a circular worktable, and the parting positioning boss is evenly arranged on the B mold. This parting facilitates patterning and molding. It is also suitable for manual bonding of patterns in current workshops and automatic bonding of automatic bonding machines.

(2) Casting structure and size In order to prevent mold deformation, measures such as adding two anti-deformation ribs on the surface of the upper cover of the mold and increasing the fillet of the product transition are taken to ensure the stability of the foam mold.

(3) Except for local special requirements, the machining allowance is uniformly set to 4mm.

(4) The shrinkage rate of this gearbox housing is 1.5%.

(5) The draft angle is set to 1 °. If it is easy to cause deformation during the partial mold removal process, and the thick movable block at the diaphragm is large, the draft angle can be increased.

(6) The feed ports are provided at both ends of the mold length at the injection position. The size of the feed port is required to match the automatic feed gun in the workshop. During the molding process, a secondary feeding method can be used to allow the beads to more fully fill the cavity. In addition, there is a relatively open top cavity and a side wall free of any obstructions at this location. The beads can be pointed directly at the end of the filling and then filled in turn.